Mine are 16 weeks and I just put some in. They climb around on them and occasionally poop in one or two. I put 2 on floor and 12 equal height to roosts, which are on opposite wall. Am going to put golf balls in several. I dont expect to see eggs before end of Nov. Since my boxes are only 12" X 12' I will have to have around 20 for the 24 birds I have. I doubt they would share a 12x12. Will end up with half on floor opposite roost wall, and half up at equal ht of roost. Suspect I need a walkboard to that bunch because I suspect chickens do not feel much like jumping up to a box when they are carrying an egg.